Transparent conductive film

ABSTRACT

A transparent conductive film is disclosed. The transparent conductive film includes a substrate and a first silver nanowire layer. The transparent conductive film has a first absorption peak at 340 nm to 400 nm and a second absorption peak at 500 nm-650 nm, and a ratio of a maximum peak intensity of the first absorption peak to a maximum peak intensity of the second absorption peak is in a range of 2 to 5.5.

RELATED APPLICATIONS

The present disclosure is a continuation of and claims priority to U.S.patent application Ser. No. 16/944,244, titled “TRANSPARENT CONDUCTIVEFILM” and filed on Jul. 31, 2020, which is incorporated herein byreference.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates to a transparent conductive film. Moreparticularly, the present disclosure relates to a transparent conductivefilm for manufacturing a touch panel.

2. Description of Related Art

Recently, the application of touch panels is becoming more extensive.More and more electronic products are equipped with touch panels toprovide the functions of direct operation or issuing commands for makingthose electronic products user-friendly. Especially, the demand forflexible touch panels is increasing; therefore, a number of flexibleconductive materials with excellent conductivity have been used toreplace conventional indium tin oxide (ITO) conductive material.

Silver nanowires having high conductivity and flexibility are anexcellent material for touch panels. Silver nanowires will produce asurface plasma resonance effect that absorbs ultraviolet light in thewavelength range of 320 nm to 420 nm; therefore, a conductive filmprepared with silver nanowires would be yellow. However, the yellowcolor of the silver nanowires will affect the color of the output imagesof a display panel when a touch panel with silver nanowires is combinedwith the display panel. Accordingly, it is important to lower theyellowness of the transparent conductive film including silver nanowiresfor improving the visibility and transmittance of the touch panel.

SUMMARY

The main object of the present disclosure is to provide a noveltransparent conductive film for lowering the yellowness of thetransparent conductive film including silver nanowires.

The transparent conductive film includes a substrate including a firstsurface and a second surface opposing to the first surface; and a firstsilver nanowire layer disposed on the first surface of the substrate,wherein the transparent conductive film has a first absorption peak in arange of 340 nm to 400 nm and a second absorption peak in a range of 500nm to 650 nm, and a ratio of a maximum peak intensity of the firstabsorption peak to a maximum peak intensity of the second absorptionpeak is in a range of 2 to 5.5.

In one embodiment, a ratio of a spectral integration area of the firstabsorption peak to a spectral integration area of the second absorptionpeak is 1.2 to 1.8.

In one embodiment, the transparent conductive film further includes acoloring agent in the substrate.

In one embodiment, the substrate includes a transparent base layer and afirst protective film, and the first protective film is disposed betweenthe transparent base layer and the first silver nanowire layer.

In one embodiment, the coloring agent is in the first protective film orthe transparent base layer.

In one embodiment, an absolute value of a CIELAB b* value of thetransparent conductive film is less than or equal to 1.5.

In one embodiment, the transparent conductive film further includes asecond silver nanowire layer disposed on the second surface of thesubstrate.

In one embodiment, the substrate further includes a second protectivefilm, the second protective film is disposed between the second silvernanowire layer and the transparent base layer, and the coloring agent isin the first protective film and the second protective film or thecoloring agent is in the transparent base layer.

In one embodiment, an absolute value of a CIELAB b* value of thetransparent conductive film is less than or equal to 2.

In one embodiment, the coloring agent is at least one selected from agroup consisting of alizarin blue, basic blue, alcohol blue,water-soluble aniline blue, azo blue, brilliant cresyl blue, bromophenolblue, carbazole blue, quinoline blue, indigo blue, resin phenol blue,methyl blue, methine blue, phthalocyanine, resazurin, benzylazuron,Prussian blue, methylene blue, thymol blue, tribenzine, leucocrystalviolet, or mixture thereof.

In one embodiment, an amount of the coloring agent is 100 to 1000 ppm.

In one embodiment, the coloring agent is leucocrystal violet.

It should be noted that the term “on” in the specification may be usedherein to describe the relative positions between components. Forexample, a first silver nanowire layer being disposed “on” a substrateincludes embodiments in which the two components are formed in directcontact, and may also include embodiments in which additional componentsmay be formed between the first silver nanowire layer and the substrate.

Furthermore, the terms “first”, “second”, and the like in thespecification may be used herein for ease of description and are notrelated to the numbers or the orders. For example, “first silvernanowire layer” and “second silver nanowire layer” can both be realizedas a “silver nanowire layer.”

In the field of the present invention, the transparent base layer or theprotective film added with the coloring agent serves as a bluecompensation layer for adjusting the yellowish silver nanowire layer toa neutral color.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the transparent conductive film of thefirst and second embodiments of the present disclosure;

FIG. 2 is a sectional view of the transparent conductive film of thethird and fourth embodiment of the present disclosure; and

FIG. 3 is an ultraviolet-visible spectroscopy (UV-VIS) absorptionspectrum of test example 1 of the present disclosure.

DETAILED DESCRIPTION

First, the transparent conductive film 1000 of the first embodiment ofthe present invention is illustrated in FIG. 1, wherein the transparentconductive film 1000 includes a substrate 1, a silver nanowire layer 2,and a coloring agent. In the present embodiment, the substrate 1includes a transparent base layer 11 and a protective film 12. Theprotective film 12 is disposed between the silver nanowire layer 2 andthe transparent base layer 11. In the present embodiment, the materialof the transparent base layer 11 is polyethylene terephthalate (PET),the protective film 12 is a hard coat layer, and the coloring agent isleucocrystal violet added in the protective film 12.

In other embodiments, the material of the transparent base layer 11 maybe, but is not limited to, glass, sapphire, polymethyl methacrylate(PMMA), polyvinyl chloride (PVC), polypropylene (PP), cyclothin polymer(COP), polyethylene naphthalate (PEN), triacetate cellulose (TAC),polycarbonate (PC), Polystyrene (PS), polyimide (PI), or the like.

In other embodiments, the silver nanowire layer 2 may further include acurable resin, wherein a paste including silver nanowires and thecurable resin are mixed in a weight ratio of 1:(0.8 to 1.2) and thencoated on the substrate 1.

In other embodiments, the protective film 12 may be a hard coat layer oran overcoat layer being formed on the surface of the transparent baselayer 11. The material of the protective film 12 may be, but is notlimited to, materials of hard coat layers or overcoat layers known inthe art.

In other embodiments, the coloring agent may be colorant known in theart. For example, the coloring agent may be at least one selected from agroup consisting of alizarin blue, basic blue, alcohol blue,water-soluble aniline blue, azo blue, brilliant cresyl blue, bromophenolblue, carbazole blue, quinoline blue, indigo blue, resin phenol blue,methyl blue, methine blue, Phthalocyanine, resazurin, benzylazuron,Prussian blue, methylene blue, thymol blue, tribenzine, leucocrystalviolet, or a mixture thereof, wherein leucocrystal violet is preferable.

The transparent conductive film of the second embodiment of the presentdisclosure is similar to that of the first embodiment, except that thecoloring agent is added in the transparent base layer 11.

The transparent conductive film 2000 of the third embodiment of thepresent disclosure is illustrated in FIG. 2, wherein the transparentconductive film 2000 includes a substrate 1, a first silver nanowirelayer 21, a second silver nanowire layer 22, and a coloring agent. Inthe present embodiment, the substrate 1 includes a transparent baselayer 11, a first protective film 121, and a second protective film 122,wherein the first protective film 121 is disposed between the firstsilver nanowire layer 21 and the transparent base layer 11 and thesecond protective film 122 is disposed between the second silvernanowire layer 22 and the transparent base layer 11. In the presentembodiment, the material of the transparent base layer 11 is PET, thefirst protective film 121 and the second protective film 122 are hardcoat layers, and the coloring agent is leucocrystal violet added in thefirst protective film 121 and the second protective film 122.

The transparent conductive film of the fourth embodiment of the presentdisclosure is similar to that of the third embodiment, except that thecoloring agent is added in the transparent base layer 11.

The yellowing level of the silver nanowire layer in the following testexamples is evaluated by CIE L*a*b* color space (also referred to asCIELAB color space). L*a*b* color space is composed of three values: L*for lightness from black (0) to white (100); a* from green (−) to red(+); and b* from blue (−) to yellow (+). That is, the b* value (alsoreferred to as a CIELAB b* value) represents the yellowing level of thetransparent conductive film before and after addition of the coloringagent as an index of yellowing adjustment.

Test Example 1

First, the present test example utilized the transparent conductive film1000 illustrated in FIG. 1 to evaluate UV-VIS spectrum of thetransparent conductive film 1000 including the silver nanowire layer 2with leucocrystal violet of different concentrations. The transparency,haze, b* value, and a* value are shown in Table 1.

TABLE 1 Resistance Content of of silver leucocrystal nanowire Trans-violet layer parency Haze b* a* (ppm) (Ω/square) (%) (%) value valueExample 1 250 30.4 91.1 1.42 1.49 −0.22 Example 2 500 33.9 90.3 1.45 0.9−0.65 Example 3 1000 34.1 88.5 1.50 −0.49 −0.95 Comparative 0 32.9 92.01.55 1.94 −0.74 example 1

The UV-VIS spectrum of Example 1 to Example 3 and Comparative example 1are shown in FIG. 3. According to the UV-VIS spectrum in FIG. 3, each ofthe groups had a first absorption peak in a range of 340 nm to 400 nm(blue), and each of the groups having leucocrystal violet added theretohad a second absorption peak in a range of 500 nm to 650 nm (yellow),wherein the maximum peak intensity and the spectral integration area ofthe first absorption peak and the second absorption peak are shown inTable 2 and Table 3.

TABLE 2 Maximum Ratio of the maximum peak Maximum peak peak intensityintensity of the first intensity of the of the second absorption peak toa first absorption absorption maximum peak intensity of peak peak thesecond absorption peak Example 1 6.43 1.20 5.35 Example 2 6.13 1.41 4.34Example 3 5.75 1.78 3.23 Comparative 5.84 1.01 5.78 example 1

TABLE 3 Spectral Spectral integration integration Ratio of a spectralarea area of the integration area of the first of the first secondabsorption peak to a spectral absorption absorption integration area ofthe peak peak second absorption peak Example 1 298 167 1.77 Example 2287 191 1.50 Example 3 274 226 1.21 Comparative 279 152 1.83 example 1

The results of the test example showed that the b* value was lowered andclose to 0 in the examples having leucocrystal violet added thereto inthe protective film 12, which means that the yellowness of thetransparent conductive film 1000 was significantly improved. Also, theratio of the maximum peak intensity of the first absorption peak (340 to400 nm) to the maximum peak intensity of the second absorption peak (500to 650 nm) must be in a range of 2 to 5.5 so that yellowness of thetransparent conductive film may be adjusted appropriately. Hence, thetransparent conductive film may present a neutral color instead of ablue color due to overcompensation.

Test Example 2

The present test example measured the transparency, haze, and b* valueof the transparent conductive film 1000 having leucocrystal violet addedthereto in different concentrations in the protective film 12 toevaluate the level of yellowing of the silver nanowire layer 2. Theresistance of the silver nanowire layer 2 in Example 4 to Example 7 andComparative example 2 to Comparative example 3 was about 65 Ω/square,and the concentration of leucocrystal violet was 0 to 2000 ppm. Theresults are shown in Table 4.

TABLE 4 Resistance of Content of silver leucocrystal nanowire Trans-violet layer parency Haze b* (ppm) (Ω/square) (%) (%) value Example 4125 65.37 91.7 1.31 0.81 Example 5 250 62.45 91.1 1.16 0.5 Example 6 50064.81 90.3 1.19 0.11 Example 7 1000 64.1 88.8 1.19 −0.91 Comparative2000 64.76 84.7 1.15 −3.52 example 2 Comparative 0 54.38 92.5 1.35 1.34example 3

The results of the test example showed that the absolute of the b*values of Example 4 to Example 7 were less than or equal to 1; hence,the yellowness of the transparent conductive film can be adjustedappropriately when the absolute of the b* value was less than or equalto 1. However, the transparent conductive film of Comparative example 2was blue due to the low b* value (−3.52). That is, if the concentrationof leucocrystal violet was too high (2000 ppm in Comparative example 2),the color of the transparent conductive film could not be adjustedappropriately. Accordingly, the present test example proved that theyellowness of the silver nanowire layer 2 may be adjusted appropriatelywhen leucocrystal violet was added in the range of 125 ppm to 1000 ppm(Example 4 to Example 7).

Test Example 3

According to the result of Test example 2, the concentration of theleucocrystal violet added in the protective film 12 was in the range of125 ppm to 1000 ppm in the present test example. The present testexample measured the transparency, haze, and b* value of the transparentconductive film of different resistances and added with leucocrystalviolet of different concentrations to evaluate the level of yellowing ofthe silver nanowire layer 2. The resistance of the silver nanowire layer2 in Example 8 to Example 11 and Comparative example 4 was about 30 to35Ω/square. The test results thereof are shown in Table 5. Theresistance of the silver nanowire layer 2 in Example 12 to Example 15and Comparative example 5 was about 50 to 55Ω/square. The test resultsthereof are shown in Table 6. The resistance of the silver nanowirelayer 2 in Example 16 to Example 19 and Comparative example 6 was about70 to 75Ω/square. The test results thereof are shown in Table 7.

TABLE 5 Resistance of Content of silver leucocrystal nanowire Trans-violet layer parency Haze b* (ppm) (Ω/square) (%) (%) value Example 8125 36.9 91.6 1.46 1.06 Example 9 250 35.1 91.1 1.37 0.9 Example 10 50034.34 90.1 1.45 0.47 Example 11 1000 34.83 88.6 1.39 −0.55 Comparative 030.37 92.1 1.42 1.56 example 4

TABLE 6 Resistance of Content of silver leucocrystal nanowire Trans-violet layer parency Haze b* (ppm) (Ω/square) (%) (%) value Example 12125 54.37 91.5 1.31 0.82 Example 13 250 54.45 91.3 1.16 0.53 Example 14500 53.81 90.4 1.19 0.12 Example 15 1000 55.1 88.7 1.19 −0.9 Comparative0 53.38 92.5 1.35 1.33 example 5

TABLE 7 Resistance of Content of silver leucocrystal nanowire Trans-violet layer parency Haze b* (ppm) (Ω/square) (%) (%) value Example 16125 76.49 92 1.1 0.71 Example 17 250 71.33 91.5 1.12 0.26 Example 18 50074.54 90.6 1.02 −0.39 Example 19 1000 73.82 89.1 0.95 −1.3 Comparative 067.8 92.5 1.19 0.94 example 6

According to the results shown in Table 5 to Table 7, the yellowness ofthe silver nanowire layer 2 of different resistances may be adjusted byadding leucocrystal violet, and the absolute value of the b* value ofthe transparent conductive film may be maintained in a range of lessthan or equal to 1.5.

Test Example 4

The present test example measured the transparency, haze, and b* valueof the transparent conductive film 1000 with different transparent baselayers 11 and added with coloring agent (leucocrystal violet) toevaluate the level of yellowing of the silver nanowire layer 2. Theresults are shown in Table 8. In Example 20, the substrate 1 includedthe transparent base layer 11 made of COP and 250 ppm of leucocrystalviolet being added to the protective film 12, wherein the silvernanowire layer 2 having 30 to 35Ω/square resistance was formed on theprotective film 12. In Comparative example 7, the substrate 1 includedthe transparent base layer 11 made of cyclic olefin polymer (COP),wherein the silver nanowire layer 2 was directly formed on thetransparent base layer 11, and the protective film 12 was omitted. InExample 21, the substrate 1 included the transparent base layer 11 madeof PET, and protective film 12 included 250 ppm of leucocrystal violet,wherein the silver nanowire layer 2 having 30 to 35Ω/square resistancewas formed on the protective film 12. In Comparative example 8, thesubstrate 1 included the transparent base layer 11, wherein the silvernanowire layer 2 was directly formed on the transparent base layer 11,and the protective film 12 was omitted.

TABLE 8 Transparency (%) Haze (%) b* value Example 20 91.3 1.32 0.26Comparative 91.7 1.36 1.08 example 7 Example 21 91.1 1.42 0.72Comparative 91.2 1.64 1.49 example 8

According to the results, the b* value of Example 20 was 0.26, which wasreduced by 76% compared with the b* value of 1.08 of Comparative example7 without leucocrystal violet. The b* value of Example 21 was 0.72,which was reduced by 51% compared with the b* of value 1.49 ofComparative example 8 without leucocrystal violet. That is, the presenttest example proved that the addition of the coloring agent to thesubstrate made of different materials could still adjust the yellownesscaused by the silver nanowire layer appropriately and made the b* valueof the transparent conductive film close to 0 while the hightransparency and low haze were maintained.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in the art may proceed with avariety of modifications and replacements based on the disclosures andsuggestions of the invention as described without departing from thecharacteristics thereof. Nevertheless, although such modifications andreplacements are not fully disclosed in the above descriptions, theyhave substantially been covered in the following claims as appended.

What is claimed is:
 1. A transparent conductive film, comprising: a substrate comprising a first surface and a second surface opposing to the first surface, wherein: the substrate comprises a first protective film, a base layer, and a second protective film, and the base layer is between the first protective film and the second protective film; and a first silver nanowire layer disposed on the first surface of the substrate, wherein: a coloring agent is present in the first protective film and the second protective film, an amount of coloring agent present in the substrate is 100 to 1000 ppm.
 2. The transparent conductive film claimed in claim 1, wherein the coloring agent is leucocrystal violet.
 3. The transparent conductive film claimed in claim 1, wherein the first protective film is between the base layer and the first silver nanowire layer.
 4. The transparent conductive film claimed in claim 1, wherein the first silver nanowire layer is in contact with the first protective film.
 5. The transparent conductive film claimed in claim 1, wherein the transparent conductive film has a first absorption peak in a range of 340 nm to 400 nm and a second absorption peak in a range of 500 nm to 650 nm.
 6. The transparent conductive film claimed in claim 1, wherein: the transparent conductive film has at least two absorption peaks, and a ratio of a maximum peak intensity of a first absorption peak of the at least two absorption peaks to a maximum peak intensity of a second absorption peak of the at least two absorption peaks is in a range of 2 to 5.5.
 7. The transparent conductive film claimed in claim 1, wherein an absolute value of a CIELAB b* value of the transparent conductive film is less than or equal to 1.5.
 8. The transparent conductive film claimed in claim 1, comprising a second silver nanowire layer disposed on the second surface of the substrate.
 9. The transparent conductive film claimed in claim 1, wherein the coloring agent is at least one selected from a group consisting of alizarin blue, basic blue, alcohol blue, water-soluble aniline blue, azo blue, brilliant cresyl blue, bromophenol blue, carbazole blue, quinoline blue, indigo blue, resin phenol blue, methyl blue, methine blue, Phthalocyanine, resazurin, benzylazuron, Prussian blue, methylene blue, thymol blue, tribenzine, leucocrystal violet, or a mixture thereof.
 10. A transparent conductive film, comprising: a substrate comprising a first surface and a second surface opposing to the first surface, wherein: the substrate comprises a coloring agent, and the coloring agent is leucocrystal violet; and a first silver nanowire layer disposed on the first surface of the substrate, wherein: the transparent conductive film has a first absorption peak in a range of 340 nm to 400 nm and a second absorption peak in a range of 500 nm to 650 nm, and a ratio of a spectral integration area of the first absorption peak to a spectral integration area of the second absorption peak is 1.2 to 1.8.
 11. The transparent conductive film claimed in claim 10, wherein an absolute value of a CIELAB b* value of the transparent conductive film is less than or equal to 1.5.
 12. A transparent conductive film, comprising: a substrate comprising a first surface and a second surface opposing to the first surface; a first silver nanowire layer disposed on the first surface of the substrate; and a second silver nanowire layer disposed on the second surface of the substrate, wherein: the substrate comprises a coloring agent, the coloring agent is leucocrystal violet, and an absolute value of a CIELAB b* value of the transparent conductive film is less than or equal to 1.5.
 13. The transparent conductive film of claim 12, wherein the transparent conductive film has a first absorption peak in a range of 340 nm to 400 nm and a second absorption peak in a range of 500 nm to 650 nm. 